U.S. patent number 7,599,363 [Application Number 11/202,895] was granted by the patent office on 2009-10-06 for method for reporting reception result of packets in mobile communication system.
This patent grant is currently assigned to Samsung Electronics Co. Ltd. Invention is credited to Jin-Bong Chang, Kyung-Hun Jang, Young-Soo Kim, Dong-Jun Lee, Jong-Ae Park.
United States Patent |
7,599,363 |
Jang , et al. |
October 6, 2009 |
Method for reporting reception result of packets in mobile
communication system
Abstract
Disclosed is a bitmap structure which enables the size of a
bitmap field containing reception result information to be
significantly reduced while fully performing its acknowledgment
function. To this end, a message region for recording indicators,
which enables reception success or failure for the maximum
allowable SN level packets treatable by block ACK to be confirmed,
is assigned. A message region for recording only the reception
results for unsuccessfully received packets is also assigned. A
receiving party confirms the unsuccessfully received packets
through the indicators, and retransmits the unsuccessfully received
packets. Also, a transmitting party provides the number of SN level
packets and the maximum number of fragmentation packets to the
receiving party. The receiving party determines an optimized bitmap
configuration scheme, and transmits the reception results for the
respective fragmentation packets to the transmitting party based on
the determined bitmap configuration scheme.
Inventors: |
Jang; Kyung-Hun (Suwon-si,
KR), Park; Jong-Ae (Yongin-si, KR), Lee;
Dong-Jun (Seoul, KR), Chang; Jin-Bong (Daejeon,
KR), Kim; Young-Soo (Seoul, KR) |
Assignee: |
Samsung Electronics Co. Ltd
(KR)
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Family
ID: |
46124048 |
Appl.
No.: |
11/202,895 |
Filed: |
August 12, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060034277 A1 |
Feb 16, 2006 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60607610 |
Sep 7, 2004 |
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Foreign Application Priority Data
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Aug 13, 2004 [KR] |
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10-2004-0064049 |
May 26, 2005 [KR] |
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10-2005-0044645 |
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Current U.S.
Class: |
370/389;
370/476 |
Current CPC
Class: |
H04L
1/1614 (20130101) |
Current International
Class: |
H04L
12/56 (20060101); H04J 3/00 (20060101) |
Field of
Search: |
;370/229,394,242,310,473,236,428,349,389,476 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2002-541726 |
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Dec 2002 |
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JP |
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2004-072288 |
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Mar 2004 |
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JP |
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WO 00/60797 |
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Oct 2000 |
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WO |
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Other References
(Technical Paper) Sanjiv Nanda, et al., "MAC Enhancements for
802.11n" IEEE802.11-04/0717r0, Jul. 2004, 2 pages, URL,
http://www.ieee802.org/11/DocFiles/04/11-04-0717-00-000n-mac-overview.ppt-
. cited by other .
(Technical Paper) John Ketchum, et al., "System Description and
Operating Principles for High Throughput Enhancements to 802.11"
IEEE802.11-04/0870r0, Aug. 2004, 4 pages including p. 31, 32, 48,
URL,
http://www.ieee802.org/11/DocFiles/04/11-04-0870-00-000n-802-11-ht-system-
-description-and-operating-principles.doc. cited by other .
(Technical Paper) Sanjiv Nanda, et al., "MAC Enhancements for
802.11n," IEEE802.11-04/0717r0, Jul. 2004, 2 pages, URL,
http://www.ieee802.org/11/DocFiles/04/11-04-0717-00-000n-mac-overview.ppt-
. cited by other .
(Technical Paper) John Ketchum, et al., "System Description and
Operating Principles for High Thoughput Enhancements to 802.11,"
IEEE802.11-04/0870r0, Aug. 2004, 4 pages including p. 31,32,48,
URL,
http://www.ieee802.org/11/DocFiles/04/11-04-0870-00-000n-802-11-ht-system-
-description-and-operating-principles.doc. cited by other.
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Primary Examiner: Taylor; Barry W
Attorney, Agent or Firm: McNealy Bodendorf LLP
Parent Case Text
PRIORITY
This application claims priority to applications entitled "Method
for Reporting Reception Results of Packets in Mobile Communication
System" filed in United States Patent and Trademark Office on Sep.
7, 2004 and assigned Ser. No. 60/607,610, and filed in the Korean
Industrial Property Office on Aug. 13, 2004 and May 26, 2005 and
assigned Serial Nos. 2004-64049 and 2005-44645, the contents of
each of which are hereby incorporated by reference.
Claims
What is claimed is:
1. A method for configuring a Block Acknowledgement (BA) frame in a
wireless communication system for acknowledgement by a receiver of
a data transmission from a transmitter, the method comprising:
receiving--by the receiver a Block Acknowledgement Request (BAR)
frame in the data transmission from the transmitter; determining by
the receiver an overall size of a bitmap for the BA frame from the
BAR frame configured to acknowledge the data transmission;
configuring by the receiver the BA frame of the response to include
the bitmap having the determined overall size; transmitting by the
receiver the configured BA frame to the transmitter, wherein the
bitmap of the BA frame includes bits representing reception results
of packets of the data transmission received from the
transmitter.
2. The method as claimed in claim 1, wherein the overall bitmap
size is determined by the receiver to be: Overall bitmap
size=ceiling [m.times.n/8]octets where ceiling [x] denotes a
minimum integer from among integers exceeding `x`, the variable `m`
is a number of consecutively received packets-, and the variable
`n` is a number of fragmentation packets, wherein the variable `m`
and the variable `n` are determined from the BAR frame.
3. The method as claimed in claim 2, wherein the bitmap of the BA
includes a plurality of individual bitmaps for the consecutively
received packets and a size of each individual bitmap corresponding
to each of the consecutively received packets is determined as n
bits.
4. The method as claimed in claim 3, wherein a number of bits out
of the overall bitmap size are padding bit, the number of padding
bits being calculated by the following equation: ceiling
[m.times.n/8].times.8-m.times.n.
5. The method as claimed in claim 1, wherein each bit of the bitmap
for the block acknowledgement is set as `1`if a corresponding
packet is successfully received, and is set as `0` if reception of
the corresponding packet has failed.
6. The method as claimed in claim 1, wherein information about
bitmap size is included in a control field of the BAR frame.
7. The method as claimed in claim 1, wherein the BAR frame includes
bitmap size related information used by the receiver in determining
the overall size of the bitmap.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a bitmap structure for reporting
reception result of packets applying a retransmission technique and
a method for transmitting/receiving the reception result in a
mobile communication system.
In general, a radio channel can cause errors in transmitted packets
under the influence of multi-path fading, interferences among
users, noises, and so forth. A solution to this problem includes a
Forward Error Correction Code (FEC) scheme in which the probability
of error occurrence is lowered by additionally sending redundant
information, an Automatic Repeat Request (ARQ) scheme in which,
when errors occurs, retransmission of packets where the errors have
occurred is requested, and a Hybrid Automatic Retransmission
Request (HARQ) scheme which combines both the schemes.
In the ARQ scheme, a receiver uses an Acknowledgment (ACK)/Not
Acknowledgment (NACK) signal for notifying a transmitter of whether
or not received packets are erroneous. The ACK signal confirms to
the transmitter that the receiver has received the corresponding
packets. In contrast, the NACK signal confirms to the transmitter
that the receiver has failed to receive the corresponding packets.
If the transmitter receives the NACK signal, the transmitter
retransmits the corresponding packets to the receiver.
In addition to the general ARQ scheme in which reception results
are acknowledged on a packet-by-packet basis, there is a block ARQ
scheme in which reception results of a plurality of transmitted
packets are acknowledged as a group through a block ARQ
message.
FIG. 1 is a diagram illustrating a basic concept of a general block
ARQ scheme based on an example which presumes that the block ARQ
scheme is applied to every three packets.
Referring to FIG. 1, a transmitter transmits three packets, that
is, Packet #1, Packet #2 and Packet #3, in sequence. The three
packets (Packet #1 to Packet #3) have the same Destination Address
(DA), for example, DA2. Each of the packets (Packet #1 to Packet
#3) is provided with a Sequence Number (SN) and a Fragmentation
Number (FN). The SN signifies the order in which packets are
transmitted from an upper layer. Even packets having the same SN
may be transmitted over a plurality of packets as occasion demands.
The FN signifies the order of transmitting the plurality of packets
divided over the transmission from packet having the one same
SN.
A receiver checks whether or not packets are continuously received
and which packets are not received by comparing the SN and the FN
of a received packet with those of previously received packets. In
the following description, packets at an SN level will be referred
to as `SN level packets`, and packets divided from the SN level
packets will be referred to as `fragmentation packets`. When a
packet is not referred to as the SN level packet or the
fragmentation packet, but simply referred to as `a packet`, it is
meant to incorporate both of the above-mentioned two types of
packets.
Of the three packets, the first and second packets (Packet #1,
Packet #2) are fragmentation packets having the same SN (e.g., SN
1) and different FNs (e.g., Frag 1, Frag 2). The third packet
(packet #3) is an SN level packet having a different SN (e.g., SN
2) from that of the first and second packets (Packet #1, Packet
#2).
In FIG. 1, it is assumed that the receiver succeeds in receiving
the first and third packets (Packet #1, Packet #3) and fails to
receive the second packet (Packet #2).
The receiver configures a block ACK message on the basis of the
reception result as stated above and transmits the configured block
ACK message to the transmitter. The block ACK message includes a
header and a payload. A Destination Address DA1 is recorded in the
header. The Destination Address DA1 is an address of the
transmitter. The reception results for the respective received
packets are recorded in the payload.
Applying the above-mentioned assumption, the ACK information is
recorded as the reception result corresponding to the first and
third packets (Packet #1, Packet #3), and NACK information is
recorded as the reception result corresponding to the second packet
(Packet #2). SNs and FNs of the corresponding packets are recorded
together in the reception results.
The transmitter receives the block ACK message. The transmitter
confirms through the block ACK message that the receiver succeeds
in receiving the first and third packets (Packet #1, Packet #3) and
failed to receive the second packet (Packet #2). Thereafter,
although not shown in FIG. 1, the transmitter retransmits the
second packet (Packet #2).
The above-mentioned scheme in which the reception results for all
the received packets are recorded in one block ACK message can be
realized in various ways. However, in order to use a message having
the shortest length, a bitmap scheme is employed.
FIGS. 2 to 4 show examples of using the bitmap scheme for
acknowledging reception results.
Referring to FIG. 2, the block ACK message includes a block ACK
starting sequence field and a bitmap field. The bitmap field
consists of N ACK report fields. `N` is a value corresponding the
maximum SN and signifies the maximum number of sequences capable of
being acknowledged. That is, `N` may be defined as the maximum
allowable number of SN level packets which can be processed by one
block ACK message.
The first SN level packet, with which a bitmap in a corresponding
message deals, is recorded in the block ACK starting sequence
field. Each of reception results for N consecutive packets starting
from the packet having the SN recorded in the block ACK starting
sequence field is recorded in the bitmap Field.
The respective ACK report fields constituting the bitmap field are
divided into (M.times.8) regions b0, b1, b2, . . . , b(n), . . . ,
b(8.times.M-1) corresponding to the number of fragmentation packets
which can be divided to the maximum extent from one SN level
packet. Hereinafter, such regions b0, b1, b2, . . . , b(n), . . . ,
b(8.times.M-1) will be referred to as `reception result information
fields`. This is because reception results are acknowledged on a
packet-by-packet basis. Thus, if the reception result is expressed
by one bit, M octets are required for the total reception results
information fields for one SN level packet, and so the bitmap field
has an overall length of M.times.N octets.
For example, when SN=1 is recorded in the block ACK starting
sequence field, the reception result for a fragmentation packet
having SN=1 and FN=n-1 will be recorded in the reception result
information field b(n) 210. If the receiver succeeds in receiving
this fragmentation packet, `1` is recorded in the reception result
information field b(n) 210. Otherwise, if the receiver fails in
receiving the fragmentation packet, `0` is recorded in the
reception result information field b(n) 210. This is based on the
assumption that `1` is an indicator bit representing reception
success and `0` is an indicator bit representing reception failure.
As another example, when `5` is recorded in the block ACK starting
sequence field, `1` is set to a third bit of the second octet if a
fragmentation packet having SN=6 and FN=3.
FIG. 3 shows the above-mentioned general example when applied to a
system based on the IEEE 802.16 standard (the 802.16), and FIG. 2
shows the same example when applied to a system based on the IEEE
802.11 e standard (the 802.11e).
A block ACK message shown in FIG. 3 includes a connection ID field,
an ACK control field and a plurality of ACK MAP fields. The ACK
control field includes a field in which a starting SN is recorded,
and a field in which the number of ACK MAPs (m) is recorded. The
ACK MAP fields are equal in number to the number of ACK MAPs (m).
The ACK MAP field has the same structure as that of the ACK report
field in FIG. 2. In FIG. 3, each of the connection ID field, the
ACK control field and the plurality of ACK MAP fields are
configured as a 2-octet field. Thus, the block ACK message has an
overall length of `(m+2).times.2`. Usually, `m` is a variable value
and the maximum number of fragmentation packets is 16 in the
802.16.
A block ACK message shown in FIG. 4 includes a BA starting sequence
control field and a BA bitmap field. Information indicating a
starting sequence recorded in the bitmap field is recorded in the
BA starting sequence control field. The BA bitmap field consists of
a plurality of ACK MAP fields. Each ACK MAP field has the same
structure as that of the ACK report field in FIG. 2. For example,
in the 802.11e, it is possible to simultaneously perform ACK
processing for a maximum of 64 SN level packets, and one SN level
packet can be divided into 16 fragmentation packets. Thus, when
each ACK MAP field is configured as a 2-octet field, the BA bitmap
field must maintain a size of 128 octets.
SUMMARY OF THE INVENTION
As stated above, if reception results are acknowledged using the
conventional bitmap scheme, a wasting of resources occurs. That is,
in conventional bitmap scheme, the bitmap is configured by taking
into consideration that the respective SN level packets will be
divided into maximum fragmentation packets. Thus, when a reception
result corresponding to an SN level packet, which is not divided
into fragmentation packets or is not divided into a maximum number
of fragmentation packets, is transmitted, reception result
information fields not used in the bitmap field occur. Such
reception result information fields may be said to be unnecessary
resources.
Accordingly, the present invention has been made to solve at least
the above-mentioned problems occurring in the prior art, and an
object of the present invention is to provide a method for
minimizing the length of a message to be transmitted.
It is a further object of the present invention to provide a method
for assigning indicator bit regions to a reception result
transmitting message, which enables an unsuccessfully received
packet to be quickly confirmed.
It is a further object of the present invention to provide a method
for transmitting only reception result information for
unsuccessfully received packets.
It is a further object of the present invention to provide a method
for confirming unsuccessfully received packets through indicator
bits corresponding to the respective packets and transmitting only
reception result information for the unsuccessfully received
packets.
It is a further object of the present invention to provide a method
for determining the size of a bitmap field, in which reception
result information is recorded, in a message transmitting the
reception result information based on the number of unsuccessfully
received packets.
It is a further object of the present invention to provide a method
for expanding message regions for transmitting reception result
information when the number of unsuccessfully received packets
exceeds a threshold value.
It is a further object of the present invention to provide a method
for optimizing the size of a bitmap by prior negotiation.
It is a further object of the present invention to provide a frame
structure for optimizing the size of a bitmap by prior
negotiation.
It is a further object of the present invention to provide a method
for transmitting the number of SN level packets and the number of
fragmentation packets from a transmitting party to a receiving
party in order to optimize the size of a bitmap.
It is a further object of the present invention to provide a method
for optimizing the size of a bitmap by the number of SN level
packets and the number of fragmentation packets.
It is a further object of the present invention to provide a frame
structure for optimizing the size of a bitmap by the number of SN
level packets and the number of fragmentation packets.
In order to accomplish these objects, in accordance with a first
aspect of the present invention, there is provided a method for
configuring a reception result reporting message for reporting to a
transmitter reception results for received packets in a receiver of
a mobile communication system in which a plurality of packets to be
consecutively transmitted are transmitted as a plurality of
fragmentation packets, the method includes recording indicators,
each of which indicates reception success or failure for each of
the received packets, in a first bitmap field of the reception
result reporting message; and creating a second bitmap field, in
which reception results corresponding to the unsuccessfully
received packets of the received packets will be recorded, in the
reception result reporting message, and recording indicator bits,
each of which indicates reception success or failure for each of
the fragmentation packets of the unsuccessfully received packets,
in the second bitmap field.
In order to accomplish the above-mentioned objects, in accordance
with a second aspect of the present invention, there is provided a
method for retransmitting packets in response to a reception result
reporting message from a receiver in a transmitter of a mobile
communication system in which a plurality of packets to be
consecutively transmitted are transmitted as a plurality of
fragmentation packets, the method includes checking if
unsuccessfully received packets exist through indicators of the
respective plural packets, which are recorded in a first bitmap
field of the reception result reporting message; identifying
unsuccessfully received fragmentation packets corresponding to the
unsuccessfully received packets through indicator bits which exist
in a second bitmap field of the reception result reporting message;
and retransmitting the unsuccessfully received fragmentation
packets or the packets including the unsuccessfully received
fragmentation packets.
In order to accomplish the above-mentioned objects, in accordance
with a third aspect of the present invention, there is provided a
method for configuring bitmaps in a mobile communication system,
the method includes receiving information about the number of
consecutively received packets and the maximum number of
fragmentation packets; and determining a bitmap configuration
scheme by the information about the number of consecutively
received packets and the maximum number of fragmentation
packets.
In order to accomplish the above-mentioned objects, in accordance
with a fourth aspect of the present invention, there is provided a
method for requesting reception results for transmitted packets in
a mobile communication system, the method includes consecutively
transmitting a predetermined number of packets (m) while the
respective packets are divided into one or more fragmentation
packets; and transmitting information about the number of
consecutively transmitted packets (m) and the number of
fragmentation packets (n).
In order to accomplish the above-mentioned objects, in accordance
with a fifth aspect of the present invention, there is provided a
method for reporting reception results for received packets in a
mobile communication system, the method includes consecutively
receiving m packets divided into one or more fragmentation packets;
receiving information about the number of consecutively received
packets (m) and the number of fragmentation packets (n);
determining a bitmap configuration scheme by the information about
the number of consecutively received packets (m) and the number of
fragmentation packets (n); configuring the bitmaps including
reception results for the respective fragmentation packets by the
determined bitmap configuration scheme; and transmitting the
bitmaps.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present
invention will be more apparent from the following detailed
description taken in conjunction with the accompanying drawings, in
which:
FIG. 1 is a diagram illustrating a basic concept of a general block
ARQ scheme;
FIGS. 2 to 4 are diagrams showing examples of acknowledging
reception results using various conventional bitmap schemes;
FIG. 5 is a diagram showing a hierarchical bitmap structure
proposed according to the present invention;
FIGS. 6 and 7 are diagrams showing examples of acknowledging
reception results when the present invention is applied t to the
802.11n;
FIG. 8 is a control flowchart for explaining operations at a
transmitting party in accordance with a preferred embodiment of the
of the present invention;
FIG. 9 is a control flowchart for explaining operations at a
receiving party in accordance with a preferred embodiment of the of
the present invention;
FIG. 10 is a diagram showing a structure of a block ACK request
frame in accordance with a preferred embodiment of the present
invention;
FIG. 11 is a diagram showing a structure of a block ACK frame in
accordance with a preferred embodiment of the present invention;
and
FIGS. 12A to 12C, 13A to 13C, and 14A to 14C are diagrams showing
operational examples in accordance with preferred embodiments of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Hereinafter, preferred embodiments of the present invention will be
described with reference to the accompanying drawings. It should be
noted that the similar components are designated by similar
reference numerals although they are illustrated in different
drawings. Also, in the following description, a detailed
description of known functions and configurations incorporated
herein will be omitted when it may obscure the subject matter of
the present invention.
The present invention proposes a message which has a structure
enabling the size of a field (bitmap field) containing information
according to reception results to be optimized while fully
performing its intrinsic function of acknowledging the reception
results. Also, the present invention proposes a message which has a
structure significantly reducing the size of the bitmap. In the
following description, a bitmap configuring method in which the
size of the bitmap is reduced by reporting only reception results
for unsuccessfully received packets will be proposed as a first
preferred embodiment. In addition, a bitmap configuring method in
which the size of the bitmap is optimized by reporting reception
results based on information provided by a transmitting party will
be proposed as a second preferred embodiment.
Hereinafter, the first preferred embodiment of the present
invention will be describe in detail with reference to the
accompanying drawings
The first embodiment of the present invention may be realized based
on two considerations.
First, a Packet Error Rate (PER) in a general wireless data
communication system is designed at a lower level. Second, packet
losses are concentrated at a specific moment rather than uniformly
distributed.
In view of the two considerations, the number of erroneous packets
may be very small and errors may concentrically occur at a specific
moment, if any. Thus, it may be expected to succeed in receiving
most packets and fail in receiving only some packets even if
reception failures occur.
If an ARQ scheme is realized such that only reception results for
unsuccessfully received packets are acknowledged, the amount of
information according to the acknowledgment of the reception
results can be greatly reduced. The reduction in the amount of
information according to the acknowledgment of the reception
results means that the size of the bitmap is reduced.
In the following detailed description, there is proposed a block
ACK message for reporting only reception results corresponding to
unsuccessfully received fragmentation packets of fragmentation
packets transmitted from an SN level packet. To this end, a field
(herein after referred to as `SN level bitmap field`) for
transmitting indicators which enables success or failure in
receiving each of the maximum allowable SN level packets treatable
by the block ACK to be confirmed is newly defined. Also, a field
(hereinafter referred to as `ACK report field`) for transmitting
concrete reception results corresponding to the unsuccessfully
received SN level packet is newly defined. Here, the concrete
reception results are indicators which enable success or failure in
receiving each of the fragmentation packets transmitted from one SN
level packet to be confirmed.
In order to configure such a block ACK message, a transmitting
party (a party having received packets) checks on an SN-by-SN basis
if unsuccessfully received packets exist. Subsequently, for the
unsuccessfully received packets, a transmitting party sets
`reception failure` to indicators corresponding to the SNs of the
unsuccessfully received packets in the SN level bitmap field. In
contrast with this, for successfully received packets, a
transmitting party sets `reception success` to indicators
corresponding to the SNs of the successfully received packets in
the SN level bitmap field.
However, when a plurality of fragmentation packets having the same
SN are received, it is not possible to confirm reception results
for the fragmentation packets by only the SN level bitmap field. In
this case, separate information enabling unsuccessfully received
fragmentation packets to be confirmed is required.
In the first embodiment of the present invention, therefore, the
ACK report fields are separately created according to the SNs of
the unsuccessfully received packets. Indicators corresponding to
the respective fragmentation packets are recorded, that is,
indicators are recorded on an FN-by-FN basis in the ACK report
fields. These indicators represents reception success or reception
failure for the fragmentation packets having the same SN. The ACK
report fields are configured by taking into consideration the
maximum number of fragmentation packets from one SN level
packet.
The transmitting party transmits the so-configured block ACK
message to a receiving party.
The receiving party (a party having transmitted packets) confirms
reception success or failure for the respective SN level packets by
checking the indicators recorded in the SN level bitmap field of
the block ACK message. When unsuccessfully received SN level
packets exist, the receiving party checks the ACK report fields
corresponding to the unsuccessfully received SN level packets. The
receiving party is notified of the unsuccessfully received
fragmentation packets through the indicators recorded in the ACK
report fields.
FIG. 5 shows a hierarchical bitmap structure proposed according to
the present invention.
Referring to FIG. 5, a block ACK message having the hierarchical
bitmap structure includes a block ACK starting sequence field and a
bitmap field. The bitmap field consist of an SN level bitmap field
and an erroneous SN packet bitmap field. The erroneous SN packet
bitmap field includes a plurality of ACK report fields (M.times.m
ACK fields). Here, `m` corresponds to the number of zeros (`0`) set
to the SN level bitmap field. `M` is the number of unsuccessfully
received SN level packets.
The SN of the first SN level packet with which bitmaps in a
corresponding message deal is recorded in the block ACK starting
sequence field. At this time, the first SN level packet may be
defined as the first SN level packet to be acknowledged through the
block ACK message. Here, it should be noted that the first SN level
packet must not be interpreted as the first unsuccessfully received
SN level packet.
Indicators (hereinafter referred to as `SN quick reference bits`)
representing the reception results (reception success or failure)
according to the respective SNs are recorded in the SN level bitmap
field. The length of the SN level bitmap field is determined by the
number of maximum allowable SN level packets that can be processed
by the block ACK. That is, if the number of maximum allowable SN
level packets that can be processed by the block ACK is 8.times.N,
the SN level bitmap field has a length of N octets (8.times.N
bits). Thus, each bit constituting the SN level bitmap field is
used as the SN quick reference bit assigned SN by SN.
The erroneous SN packet bitmap field includes ACK report fields.
Since the ACK report fields are separately created according to the
SNs of the unsuccessfully received packets, the number of ACK
report fields must be equal to the number of the unsuccessfully
received SN level packets. Thus, the erroneous SN packet bitmap
field has a length of M.times.m octets. Here, M octets, the overall
length of the ACK report fields, is a fixed value, so the overall
length of the erroneous SN packet bitmap field (M.times.m octets)
is determined by the number of the unsuccessfully received SN level
packets (m).
For example, the greater the number of the unsuccessfully received
SN level packets (m), the longer the overall length of the
erroneous SN packet bitmap field (M.times.m octets). In contrast
with this, the lesser the number of unsuccessfully received SN
level packets (m), the shorter the overall length of the erroneous
SN packet bitmap field (M.times.m octets). If there are no
unsuccessfully received SN level packets, the erroneous SN level
packet bitmap field may not exist.
A mapping relation between the ACK report fields and the SN quick
reference bits set as `0` can be established in various ways. In
the simplest example, the ACK report fields are sequentially mapped
corresponding to the SN order of the SN quick reference bits.
For example, if it is assumed that a value of the block ACK
starting sequence field is 5 and a value of the SN level bitmap
field is 11101011, two ACK report fields exist in the erroneous SN
packet bitmap field. A first of the two ACK report fields becomes a
bitmap of an SN level packet having SN=8, and a second becomes a
bitmap of an SN level packet having SN=10. Also, a scheme in which
indicators are assigned to the ACK report fields may be
employed.
Indicators for reporting reception results for the respective
fragmentation packet are recorded in the ACK report fields. Thus,
the indicators exist corresponding to the maximum number of
fragmentation packets that one SN level packet (M.times.8) can be
divided into. This is because the reception results are
acknowledged on a fragmentation packet-by-fragmentation packet
basis. In FIG. 5, the indicators are designated by `b0, b1, b2, . .
. , b(n), . . . , b(8.times.M-1)`. For example, if the indicator is
expressed by one bit, one ACK report field has a length of M
octets.
Hereinafter, a description will be given for an example of actually
configuring the block ACK message having the structure as shown in
FIG. 5.
When all fragmentation packets divided from an SN level packet
having SN=n+1 are successfully received, an (n+1)-th SN quick
reference bit b(n) in the SN level bitmap field is set as `1`.
However, when even one fragmentation packet is unsuccessfully
received, the an (n+1)-th SN quick reference bit b(n) in the SN
level bitmap field is set as `0`. That is, when even one
fragmentation packet is unsuccessfully received, a quick reference
bit corresponding to the SN of the unsuccessfully received
fragmentation packet is set as "reception failure". In this case,
there must be provided separate information which enables the
unsuccessfully received fragmentation packets to be confirmed.
If it is assumed that a fragmentation packet having SN=n+1 and
FN=n+1 is unsuccessfully received, an (n+1)-th SN quick reference
bit, that is, b(n) in the SN level bitmap field, is set as `0`, and
an ACK report field (hereinafter referred to as `m-th ACK report
field`) to be mapped to b(n) is assigned to the SN packet bitmap
field. Subsequently, a bit representing reception failure is set to
an (n+1)-th indicator b(n) in the m-th ACK report field. At this
time, a bit representing reception success is set to the remaining
indicators except the (n+1)-th indicator b(n) in the m-th ACK
report field. As an example, `0` is used as the indicator
representing reception failure and `1` is used as the indicator
representing reception success.
FIGS. 6 and 7 show examples of a message for reporting reception
results when the present invention as described above is applied to
a system based on the IEEE 802.11n standard (the 802.11n). The
examples shown in FIGS. 6 and 7 are distinguished from each other
by the number of unsuccessfully received packets. That is, if the
number of unsuccessfully received MAC service data unit (MSDUs)
does not reach a threshold value (e.g., 12), a message structure
shown in FIG. 6 is employed. However, if the number of
unsuccessfully received MSDUs is equal to or greater than the
threshold value (e.g., 12), a message structure shown in FIG. 7 is
employed.
Referring to FIG. 6, the block ACK message includes a BA control
field, a BA starting sequence control field and a BA erroneous
MSDUs' bitmap field.
The BA control field has a length of 2 octets. The BA control field
includes a BA MSDUs' bitmap field and a TID field. The BA MSDUs'
bitmap field consists of quick reference bits for representing
reception success or failure for the respective SN level packets.
The BA MSDUs' bitmap field is a region which has not been used in
the existing 802.11 and is reused for the present invention. Since
FIG. 6 supposes a case where the number of unsuccessfully received
MSDUs is below 12, the BA MSDUs' bitmap field is configured with a
size of 12 bits.
In addition, any one bit in the BA control field can be assigned
for a message indicator. As an example, the first one bit of the BA
control field may be assigned for the message indicator. The
message indicator indicates a message type. In FIG. 6, `1` is used
as the message indicator.
The SN of the first SN level packet with which bitmaps in a
corresponding message deal is recorded in the BA starting sequence
control field. The first SN level packet is a packet which is
transmitted first from among consecutively transmitted packets for
the block ACK, and it should be noted that the first SN level
packet is not the first unsuccessfully received SN level
packet.
The BS erroneous MSDUs' bitmap field consists of a plurality of ACK
MAP fields not exceeding 11 in number. The BA erroneous MSDUs'
bitmap field has the same structure and function as those of the
erroneous SN packet bitmap field described above with reference to
FIG. 5, thus, a detailed description of the BA erroneous MSDUs'
bitmap field will be omitted.
Referring to FIG. 7, the block ACK message includes a BA control
field, a BA starting sequence control field, a BA MSDUs' bitmap
field and a BA erroneous MSDUs' bitmap field.
Any one bit in the BA control field is assigned for a message
indicator. As an example, the first one bit of the BA control field
may be assigned for the message indicator. In FIG. 7, `0` is used
as the message indicator. In addition, another one bit in the BA
control field is assigned for a success indicator. The success
indicator indicates that all packets (64 MSDUs' are assumed in FIG.
7) are successfully received (designated by `A` in the drawing).
When all SN level packets are successfully received, the success
indicator is set as `1`. However, when even one SN level packet is
unsuccessfully received, the success indicator is set as `0`. If
the success indicator is set as `1`, the BS MSDUs' bitmap field and
the BA erroneous packet bitmap field are not needed.
The BA MSDUs' bitmap field carries out the same function as that of
the BA MSDUs' bitmap field existing in the BA control field as
shown in FIG. 6, so a detailed description thereof will be omitted.
The only difference between both the BA MSDUs' bitmap fields is
that the BA MSDUs' bitmap field in FIG. 7 has a size of 64 bits (8
octets) so as to represent reception success or failure for 64
packets.
The BA erroneous MSDUs' bitmap field consists of ACK MAP fields
corresponding to the number of unsuccessfully received packets. The
BA erroneous MSDUs' bitmap field has the same structure and
function as those of the erroneous SN packet bitmap field described
above with reference to FIG. 5, thus, a detailed description of the
BA erroneous MSDUs' bitmap field will also be omitted.
Hereinafter, a second preferred embodiment of the present invention
will be describe in detail with reference to the accompanying
drawings.
The second embodiment of the present invention premises a system
for transmitting a block ACK request frame together with
consecutive data frames from a transmitting party to a receiving
party. The block ACK request frame includes information needed for
transmitting the reception results of the respective data frames.
The block ACK request frame may be transmitted before or after the
transmission of the data frames. Of course, it is possible to
simultaneously transmit the block ACK request frame and the data
frames.
The receiving party receives the data frames and the block ACK
request frame. The receiving party determines a bitmap
configuration scheme on the basis of the information received
through the block ACK request frame, and then configures the
bitmaps according to the determined bitmap configuration scheme
such that the bitmaps include reception results for the data
frames. The bitmaps are acknowledged to the transmitting party
through a bloc ACK frame.
In the second embodiment of the present invention, information
about `the number of SN level packets to be consecutively
transmitted (m)` and `the maximum number of fragmentation packets
(n)` are transmitted through the block ACK request frame. Usually,
the SN level packet is transmitted having been divided into a
plurality of fragmentation packets, if necessary. The maximum
number of fragmentation packets (n) is the maximum number of
fragmentation packets that can be made from the SN level packets to
be transmitted.
In the following description, an operation for transmitting the
block ACK request frame at the transmitting party and a structure
of the block ACK request frame will be discussed in detail. Also,
an operation for reporting reception results on a fragmentation
packet-by-fragmentation packet basis through the block ACK frame at
the receiving party and a structure of the block ACK frame will be
discussed in detail.
Furthermore, in an example of the present invention, there will be
discussed an operation performed when the number of packets to be
consecutively transmitted (m) and the maximum number of
fragmentation packets are randomly given.
Hereinafter, the operations of the transmitting and receiving
parties in accordance with preferred embodiments of the present
invention will be described in detail.
FIG. 8 shows a control flow for explaining the operation of the
transmitting party in accordance with a preferred embodiment of the
present invention.
Referring to FIG. 8, in step 810, the number of packets to be
transmitted (m) is determined. The determination of `m` is effected
by the number of SN level packets to be consecutively transmitted.
Each SN level packet may be transmitted dividedly into plural
fragmentation packets. In step 812, the maximum number of
fragmentation packets is determined, or in other words the division
status of each SN level packet is confirmed. That is, the numbers
of fragmentation packets divided from the respective SN level
packets are detected and the SN level packet, from which the most
fragmentation packets are divided, is determined. The number of
fragmentation packets divided from the found SN level packet is
determined as the maximum number of fragmentation packets (n).
In step 814, the Block ACK Request (BAR) frame is configured such
that `m` and `n` as determined above are included in the BAR frame.
At this time, the SN of the first SN level packet to be transmitted
is recorded in the block ACK starting sequence control field of the
BAR frame. The transmitting party transmits the BAR frame to the
receiving party. A structure of the BAR frame will be discussed
with respect to FIG. 10.
Although not shown in FIG. 8, m SN level packets may be transmitted
before or after the transmission of the corresponding BAR frame. Of
course, it is possible to simultaneously transmit the SN level
packets with the BAR frame. Also, the receiving party provides to
the transmitting party the reception results corresponding to the
respective fragmentation packets of m SN level packets. The
reception results, on a fragmentation packet-by fragmentation
packet basis, are provided through the Block ACK (BA) frame. The
transmitting party retransmits the fragmentation packets based on
the reception results for the respective fragmentation packets
acquired through the BA frame.
FIG. 9 shows a control flow for explaining the operation of the
receiving party in accordance with a preferred embodiment of the
present invention.
Referring to FIG. 9, in step 910, the receiving party receives the
BAR frame. In step 912, the receiving party confirms `m` and `n`
from the BAR frame.
Once the receiving party confirms `m` and `n`, it determines a
bitmap configuration scheme through steps 914 to 918. The bitmap
configuration scheme is determined by the overall bitmap size, the
bitmap size corresponding to one SN level packet and the number of
bits to be padding-processed.
In step 914, the overall bitmap size is determined. The overall
bitmap size is determined by `m` and `n` previously confirmed in
step 912. As an example, the overall bitmap size can be determined
by Equation (1) as follows: Overall bitmap size=ceiling
[m.times.n/8]octets (1) where ceiling [x] denotes a minimum integer
from among integers exceeding `x`. The overall bitmap size may also
be expressed as the overall bitmap size in bit by multiplying the
overall bitmap size in octet by `8`.
For example, if `m` is 2 and `n` is 7, the overall bitmap size is
expressed by `ceiling [1.75]`. Since `ceiling [1.75]` denotes a
minimum integer from among integers larger than `1.75`, it results
in `2`. Thus, the overall bitmap size is determined as 2
octets.
In step 916, the bitmap sizes to be assigned to the respective SN
level packets are determined. Preferably, the same bitmap size is
assigned to all the SN level packets. When the same bitmap size is
assigned in this way, the bitmap size for only one SN level packet
is determined and the determined bitmap size can be applied to the
remaining SN level packets. For example, the bitmap size is
determined as `n` previously confirmed in step 912. This is because
reception results must be acknowledged on a fragmentation
packet-by-fragmentation packet basis.
According to the above-mentioned description, the sum of the bitmap
sizes to be assigned to the respective SN level packets dos not
exceed the overall bitmap size. That is, when the bitmap sizes are
assigned to the respective SN level packets, the sum of the bitmap
sizes is equal to the overall bitmap size or the remaining bits
occur. In step 918, the number of bits to be padding-processed is
determined. However, when the sum of the bitmap sizes assigned to
the respective SN level packets is equal to the overall bitmap
size, there is no remaining bit, and no padding is required. The
number of bits to be padded can be generalized by Equation (2) as
follows: ceiling [m.times.n/8].times.8-m.times.n (2)
The unit of Equation (2) is a bit. The bitmap configuration scheme
is determined by the overall bitmap size, the bitmap sizes
according to the respective SN level packets and the number of bits
to be padding-processed previously determined through steps 914 to
918. Also, bit values according to the reception results on a
fragmentation packet-by-fragmentation packet basis are inserted in
corresponding bit positions. As for the bit positions, refer to SNs
and FNs which the fragmentation packets have `1 (success)` and `0
(failure)` are used as the bit values according to the reception
results.
The bitmap structure will be described with reference to FIG. 11.
Examples of inserting the bit values according to the reception
results for the respective fragmentation packets in the
corresponding bit positions are illustrated in FIGS. 12 to 14.
These examples will also be described later in detail.
In step 922, the BA frame including the bitmaps is configured and
transmitted to the transmitting party.
Hereinafter, a structure of the BAR frame transmitted from the
transmitting party in accordance with the second embodiment of the
present invention will be described in detail.
The structure of the BAR frame proposed in the second embodiment of
the present invention is characterized in that it includes
information about the number of SN level packets to be
consecutively transmitted (m) and the number of fragmentation
packets of the SN level packet divided the most (n).
FIG. 10 illustrates a structure of the BAR frame, on which the
above-mentioned characteristic is reflected.
Referring to FIG. 10, the BAR frame includes a BAR control field
and a BA starting sequence control field. The sizes of the BAR
control field and the BA starting sequence control field are 2
octets each.
The BAR control field includes a `Num of MSDUs` field and a `Max.
num of Frag` field. The number of SN level packets to be
consecutively transmitted (m) is recorded in the `Num of MSDUs`
field. The number of fragmentation packets of the SN level packet
divided the most (n) is recorded in the `Max. num of Frag` field.
The size of the `Num of MSDUs` field is 6 bits, and the size of the
`Max. num of Frag.` Field is 4 bits.
The SN of the first SN level packet to be transmitted from among
the consecutively transmitted SN level packets is recorded in the
BA starting sequence control field.
Hereinafter, a structure of the BA frame transmitted to the
receiving party in accordance with the second embodiment of the
present invention will be described in detail.
The structure of the BA frame proposed in the second embodiment of
the present invention is characterized in that it has a bitmap
structure which is optimized using `m` and `n` provided from the
transmitting party.
FIG. 11 illustrates a structure of the BA frame, on which the
above-mentioned characteristic is reflected.
Referring to FIG. 11, the BA frame includes a BA starting sequence
control field and a BA bitmap field.
The most preceding SN level packet from among the consecutively
received SN level packets is recorded in the BA starting sequence
control field.
The overall size of the BA bitmap field is determined by Equation
(1). That is, the overall size of the BA bitmap field can be
determined by `m` and `n` received through the BAR frame. The BA
bitmap field consists of m bitmaps. Each of m bitmaps is configured
with a size of n bits. Each bit constituting the bitmaps represents
a reception result of a corresponding fragmentation packet. Each of
the bitmaps corresponds to one of the consecutively received SN
level packets, and a reception result for the corresponding SN
level packet is recorded in the bitmap. At this time, a bit
position, in which the reception result for the fragmentation
packet is recorded within the bitmap, is assigned by the SN and the
FN of the fragmentation packet. The remaining bits, which are not
used as the bitmaps in the BA bitmap field, are subjected to the
padding processing. The number of bits to be padded can be derived
by Equation (2).
Hereinafter, case-by-case operations in accordance with the second
embodiment of the present invention will be described.
FIGS. 12A to 12C are views for explaining an operational example in
a case where all SN level packets consecutively transmitted from
the transmitting party are successfully received.
FIG. 12A shows that three SN level packets (SN=10, 11, 12) are
consecutively transmitted. Here, the SN level packet having SN=10
are divided into four fragmentation packets 10-1, 10-2, 10-3, 10-4,
the SN level packet having SN=11 are divided into three
fragmentation packets 11-1, 11-2, 11-3, and the SN level packet
having SN=12 are divided into five fragmentation packets 12-1,
12-2, 12-3, 12-4, 12-5. Thus, `m` is determined as `3`, and `n` is
determined as `5`. The reason why `n` is determined as `5` is that
the number of fragmentation packets divided the most from one SN
level packet is `5`.
FIG. 12B shows a BAR frame structure in which m=`3` and n=`5` are
set in the BAR control field. The SN of a SN level packet which is
transmitted first from among the three consecutively transmitted SN
level packets is `10`. Thus, `10` is recorded in the BA starting
sequence control field.
If the receiving party receives the BAR frame having the structure
as shown in FIG. 12B, it confirms information recorded in the BAR
control field and the BA starting sequence control field. Hereby,
the receiving party recognizes that the three SN level packets
having SNs of 10, 11 and 12 are consecutively transmitted and the
number of fragmentation packets divided the most is `5`.
Subsequently, the receiving party determines the overall bitmap
size by Equation (1). According to Equation (1), the overall bitmap
size is determined as 2 octets (16 bits). Indicator bits indicating
reception results corresponding to the respective SN level packets
are determined as a 5-bit indicator bit. This is because the SN
level packet having SN=12 is divided into five fragmentation
packets and at least 5 bits are required for indicating reception
results on a fragmentation packet-by-fragmentation packet
basis.
The four fragmentation packets constituting the SN level packet
having SN=10 have been all successfully received. Thus, the
indicator bit indicating the reception result for the SN level
packet having SN=10 is set as `11110` (designated by {circle around
(1)} in FIG. 12C). The upper four bits set as `1` indicate that the
respective fragmentation packets have been successfully received.
The last bit is set as `0` because there is no fragmentation packet
corresponding to that bit.
The three fragmentation packets constituting the SN level packet
having SN=11 have been all successfully received. Thus, the
indicator bit indicating the reception result for the SN level
packet having SN=11 is set as `11100` (designated by {circle around
(2)} in FIG. 12C). The upper three bits set as `1` indicate that
the respective fragmentation packets have been successfully
received. The lower 2 bits are set as `0` because there is no
fragmentation packet corresponding to those bits.
The five fragmentation packets constituting the SN level packet
having SN=12 have been all successfully received. Thus, the
indicator bit indicating the reception result for the SN level
packet having SN=12 is set as `11111` (designated by {circle around
(3)} in FIG. 12C). The five bits set as `1` indicate that the
respective fragmentation packets have been successfully
received.
Once the 5-bit indicator bits indicating the reception results for
the respective SN level packets are assigned, the remaining bit of
1 bit occurs in the bitmap the overall size of which has been
determined as 2 octets (16 bits). This is determined by Equation
(2). The receiving party performs padding for the remaining bit.
That is, the remaining bit is set as `0`.
In conclusion, the reception result for the three consecutively
transmitted SN level packets is determined as `11110 11100 11111
0`. The determined reception result is recorded in the BA bitmap
field of the BA frame. Also, `10` is recorded in the BA starting
sequence control field of the BA frame.
FIGS. 13A to 13C and FIGS. 14A to 14C are views for explaining
operational examples in a case where some SN level packets are
unsuccessfully received from among SN level packets consecutively
transmitted from the transmitting party.
FIG. 13A shows that three SN level packets (SN=10, 11, 12) are
consecutively transmitted. Here, the SN level packet having SN=10
are divided into four fragmentation packets 10-1, 10-2, 10-3, 10-4,
the SN level packet having SN=11 are divided into three
fragmentation packets 11-1, 11-2, 11-3, and the SN level packet
having SN=12 are divided into five fragmentation packets 12-1,
12-2, 12-3, 12-4, 12-5. Thus, `m` is determined as `3`, and `n` is
determined as `5`. The reason why `n` is determined as `5` is that
the number of fragmentation packets divided the most from one SN
level packet is `5`. Among the fragmentation packets, the
fragmentation packets corresponding to 11-2, 12-2 and 12-4 have
been unsuccessfully received.
FIG. 13B shows a BAR frame structure in which m=`3` and n=`5` are
set in the BAR control field. The SN of a SN level packet to be
transmitted first is `10`. Thus, `10` is recorded in the BA
starting sequence control field.
If the receiving party receives the BAR frame having the structure
as shown in FIG. 13B, it confirms information recorded in the BAR
control field and the BA starting sequence control field. Hereby,
the receiving party recognizes that the three SN level packets
having SNs of 10, 11 and 12 are consecutively transmitted and the
number of fragmentation packets divided the most is `5`.
Subsequently, the receiving party determines the overall bitmap
size by Equation (1). According to Equation (1), the overall bitmap
size is determined as 2 octets (16 bits). Indicator bits indicating
reception results corresponding to the respective SN level packets
are determined as a 5-bit indicator bit. This is because the SN
level packet having SN=12 is divided into five fragmentation
packets and at least 5 bits are required for indicating reception
results on a fragmentation packet-by-fragmentation packet
basis.
The four fragmentation packets 10-1, 10-2, 10-3, 10-4 constituting
the SN level packet having SN=10 have been all successfully
received. Thus, the indicator bit indicating the reception result
for the SN level packet having SN=10 is set as `11110` (designated
by {circle around (1)} in FIG. 13C). The upper four bits set as `1`
indicate that the respective fragmentation packets have been
successfully received. The last bit is set as `0` because there is
no fragmentation packet corresponding to that bit.
Of the three fragmentation packets 11-1, 11-2, 11-3 constituting
the SN level packet having SN=11, the fragmentation packets
corresponding to 11-1 and 11-3 have been successfully received, but
the fragmentation packet corresponding to 11-2 has been
unsuccessfully received. Thus, the indicator bit indicating the
reception result for the SN level packet having SN=11 is set as
`10100` (designated by {circle around (2)} in FIG. 13C). The bits
set as `1` indicate that the corresponding fragmentation packets
11-1, 11-3 have been successfully received. In contrast with this,
the bit set as `0` indicates that the corresponding fragmentation
packet 11-2 has been unsuccessfully received. The lower 2 bits are
set as `0` because there is no fragmentation packet corresponding
to those bits.
Of the five fragmentation packets 12-1, 12-2, 12-3, 12-4, 12-5
constituting the SN level packet having SN=12, the fragmentation
packets corresponding to 12-1, 12-3 and 12-5 have been successfully
received, but the fragmentation packets corresponding to 12-2 and
12-4 have been unsuccessfully received. Thus, the indicator bit
indicating the reception result for the SN level packet having
SN=12 is set as `10101` (designated by {circle around (3)} in FIG.
13C). The bits set as `1` indicate that the corresponding
fragmentation packets 12-1, 12-3, 12-5 have been successfully
received. In contrast with this, the bits set as `0` indicate that
the corresponding fragmentation packets 12-2, 12-4 have been
unsuccessfully received.
Once the 5-bit indicator bits indicating the reception results for
the respective SN level packets are assigned, the remaining bit of
1 bit occurs in the bitmap the overall size of which has been
determined as 2 octets (16 bits). This is determined by Equation
(2). The receiving party performs padding for the remaining bit.
That is, the remaining bit is set as `0`.
In conclusion, the reception result for the three consecutively
transmitted SN level packets is determined as `11110 10100 10101
0`. The determined reception result is recorded in the BA bitmap
field of the BA frame. Also, `10` is recorded in the BA starting
sequence control field of the BA frame.
FIG. 14A shows that two SN level packets (SN=10, 11) are
consecutively transmitted. Here, the SN level packet having SN=10
are divided into seven fragmentation packets 10-1, 10-2, 10-3,
10-4, 10-5, 10-6, 10-7, and the SN level packet having SN=11 are
divided into five fragmentation packets 11-1, 11-2, 11-3, 11-4,
11-5. Thus, `m` is determined as `2`, and `n` is determined as `7`.
The reason why `n` is determined as `7` is that the number of
fragmentation packets divided the most from one SN level packet is
`7`. Among the fragmentation packets, the fragmentation packets
corresponding to 10-3, 10-6 and 11-2 have been unsuccessfully
received.
FIG. 14B shows a BAR frame structure in which m=`2` and n=`7` are
set in the BAR control field. The SN of a SN level packet to be
transmitted first is `10`. Thus, `10` is recorded in the BA
starting sequence control field.
If the receiving party receives the BAR frame having the structure
as shown in FIG. 14B, it confirms information recorded in the BAR
control field and the BA starting sequence control field. Hereby,
the receiving party recognizes that the two SN level packets having
SNs of 10 and 11 are consecutively transmitted and the number of
fragmentation packets divided the most is `7`.
Subsequently, the receiving party determines the overall bitmap
size by Equation (1). According to Equation (1), the overall bitmap
size is determined as 2 octets (16 bits). Indicator bits indicating
reception results corresponding to the respective SN level packets
are determined as a 7-bit indicator bit. This is because the SN
level packet having SN=10 is divided into seven fragmentation
packets and at least 7 bits are required for indicating reception
results on a fragmentation packet-by-fragmentation packet
basis.
Of the seven fragmentation packets 10-1, 10-2, 10-3, 10-4, 10-5,
10-6, 10-7 constituting the SN level packet having SN=10, the
fragmentation packets corresponding to 10-1, 10-2, 10-4, 10-5 and
10-7 have been successfully received, but the fragmentation packet
corresponding to 10-3 and 10-6 have been unsuccessfully received.
Thus, the indicator bit indicating the reception result for the SN
level packet having SN=10 is set as `1101101` (designated by
{circle around (1)} in FIG. 14C). The bits set as `1` indicate that
the corresponding fragmentation packets 10-1, 10-2, 10-4, 10-5,
10-7 have been successfully received. In contrast with this, the
bits set as `0` indicate that the corresponding fragmentation
packet 10-3, 10-6 have been unsuccessfully received.
Of the five fragmentation packets 11-1, 11-2, 11-3, 11-4, 11-5
constituting the SN level packet having SN=11, the fragmentation
packets corresponding to 11-1, 11-3, 11-4 and 11-5 have been
successfully received, but the fragmentation packet corresponding
to 11-2 has been unsuccessfully received. Thus, the indicator bit
indicating the reception result for the SN level packet having
SN=11 is set as `1011100` (designated by {circle around (2)} in
FIG. 14C). The bits set as `1` indicate that the corresponding
fragmentation packets 11-1, 11-3, 11-4, 11-5 have been successfully
received. In contrast with this, the bit set as `0` indicates that
the corresponding fragmentation packet 11-2 has been unsuccessfully
received. The lower 2 bits are set as `0` because there is no
fragmentation packet corresponding to those bits.
Once the 7-bit indicator bits indicating the reception results for
the respective SN level packets are assigned, the remaining bits of
2 bits occur in the bitmap the overall size of which has been
determined as 2 octets (16 bits). This is determined by Equation
(2). The receiving party performs padding for the remaining bits.
That is, the remaining bits are set as `0`.
In conclusion, the reception result for the three consecutively
transmitted SN level packets is determined as `1101101 1011100 00`.
The determined reception result is recorded in the BA bitmap field
of the BA frame. Also, `10` is recorded in the BA starting sequence
control field of the BA frame.
In the above-mentioned second embodiment of the present invention,
it is assumed that the transmitting party provides the number of SN
level packets to be consecutively transmitted and the maximum
number of fragmentation packets to the receiving party in order to
negotiate the bitmap size in advance. However, the present
invention can be realized in such a manner that the receiving party
confirms the number of consecutively transmitted SN level packets
and the maximum number of fragmentation packets by receiving the
consecutively transmitted SN level packets. In this way, there is
no need for transmitting the block ACK request (BAR) frame at the
transmitting party.
As described above, the present invention makes it possible to
efficiently use transmission resources by providing a hierarchical
bitmap structure. Also, in view of an actual communication
environment, it may be expected to not only enhance gains in the
transmission resources, but also have a great effect on performance
of a mobile communication system. Furthermore, by negotiating the
bitmap size in advance through the block ACK request, the number of
bits for reporting reception results can be optimized. This results
in effective using of the transmission resources and performance
improvement of a mobile communication system.
While the invention has been shown and described with reference to
certain preferred embodiments thereof, it will be understood by
those skilled in the art that various changes in form and details
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims.
* * * * *
References